The following is a tabulation of some prior art that presently appears relevant:
U.S. patentsU.S. Pat. No.Kind CodeIssue DatePatentee7,168,948B22007 Jan. 30 Swearingen7,214,054B22007 May 8 BoulachanisU.S. Patent Application PublicationsPublication NumberKind CodePubl. DatePatentee20130157208A12013 Jun. 20 Kazadi20040265763A12004 Dec. 30 BoulachanisForeign Patent DocumentsPat. No.Kind CodeIssue DatePatenteeCN 203757676U2014 Aug. 6  CN203177136U2013 Sep. 4  CN203757677U2014 Aug. 6  